The role of a specific bacterium as the possible etiologic agent of gastritis or peptic ulcer is supported by a growing scientific literature. However, the difficulty of conventional sampling and diagnostic techniques have restricted advances in disease diagnosis. The purpose of this Phase I project is to develop a DNA probe from the chromosomal DNA of Campylobacter pyloridis, a microorganism recently shown to be associated with gastritis and peptic ulcer. The 32P-labeled probe will be hybridized to cultured bacterial DNA immobilized on nitrocellulose. The hybridization specificity will be evaluated in the standard NaCl solution and in a new salt solution, tetraethylammonium chloride (TEAC1). The TEACl system abolishes the preferential melting of A-T vs. G-C base pairs in DNA hybrids, yielding a significant sharpening of the melting profile (less than 1C in TEACl vs. 5-15C in NaCl), thus enhancing probe specificity. A DNA probe in a TEACl salt system allows the development of a sensitive and specific DNA probe assay. The long-term objective of the project is to provide a simple, rapid, accurate and low-cost method for the detection of Campylobacter pyloridis in clinical isolates from patients with gastritis or peptic ulcer. A diagnostic test will be produced commercially for use by clinical diagnostic laboratories.